Effect of heterogeneity on engineered water injection in carbonates using five-spot sector model: A numerical study

One of the promising and emerging enhanced oil recovery techniques in both sandstones and carbonates is engineered water injection (EWI). However, few studies discussed the field-scale applications of this technique in heterogeneous carbonate formations. This paper is an extension of our previous work of the EWI technology at core-scale. This research numerically investigates heterogeneity effect on EWI technique in carbonates at field-scale using five-spot models. Three synthetic five-spot sector models were considered including homogeneous, heterogeneous with permeability channeling, and heterogeneous with gravity underride. The results showed that EWI improves both volumetric and displacement sweep efficiencies compared to conventional formation water injection (FWI) for all models investigated. Also, tracer method is recommended for better estimation of volumetric sweep efficiency as opposed to fractional flow method. Moreover, secondary EWI outperforms other techniques including secondary FW and tertiary EWI. In addition, the observed delay in tertiary EWI can be reduced by increasing well injection pressure and sulfate concentration in the engineered water. An optimum sulfate concentration of 25,000 ppm is recommended for achieving the highest oil recovery by EWI. This study gives more insight into understanding the performance of the EWI technique at field-scale. Recommendations for boosting the performance of this technique have been discussed, which assure more certainty and lower risk.